The present invention relates to a device for pneumatic knotless splicing of threads or yarns, to be installed on textile machines, in particular on automatic spoolers.
The invention is based on a device of this type known from U.S. Pat. No. 5,680,751, or from the corresponding patent DE 196 10 818, from which known device the device according to the invention takes and maintains all the prerogatives and main characteristics, in particular those of permitting remote centralised regulation of the basic parameters of the splicing cycle, such as the duration both of the jet of compressed air used for preparation and pre-treatment of the ends of the thread or yarn to be joined, and of the jet of compressed air used in the splicing chamber, for execution of the knotless pneumatic splicing of the ends of the thread or yarn, and the length of overlapping of the prepared ends of the thread or yarn at the moment of splicing.
In the known device, the compressed air is admitted into the splicing chamber, and optionally also the compressed air is admitted into the units for preparation of the ends of the thread or yarn to be joined, by means of solenoid valves which can be controlled separately, remotely from the device, thus making the device to some extent dependent on other units of the textile machine on which the splicing device is installed.
The object of the present invention is mainly to eliminate this dependence of the splicing device on other units installed on the textile machine, thus making it independent from separate solenoid valves, which are remote from the points of use of the jets of compressed air.
For its actuation, like the known device, the splicing device according to the invention also comprises its own small, reversible electric stepper motor, which can be controlled remotely by electric pulses, in order to give rise to rotation in steps from a starting position, in a forward direction, and then, after a specific number of advance steps, to rotation in a direction of return, of a set of drum control cams, and of a cam in this set which controls the movement of the levers to draw the ends of the yarn or thread from the preparation units, in the direction of the splicing chamber, the said cam having a profile which increases progressively, and preferably in steps.
In order to achieve the above-described object of making the splicing device independent from separate units of the machine on which the device is installed, and in particular from a distinct, separate solenoid valve to control the intake of the jet of compressed air into the splicing chamber, according to the invention the device is provided with a slide valve which can be actuated by a specific cam in the set of drum cams, which cam is divided, for a limited section, into two parallel branches, the first in order to give rise, during rotation of the cam drum in the forward direction, to displacement of the rod of the slide valve in one direction, and the second, in order to give rise, during rotation of the cam drum in the direction of return, to displacement of the rod of the slide valve in the opposite direction, a specific amount of free play also being provided in the lever transmission, between the said cam with an increasing profile and the drawing levers, and the drawing levers being provided with braking means, in order to keep them stopped in the displaced position, on completion of the forward rotation of the cam drum.